Translation

BG 4.37: As a kindled fire reduces wood to ashes, O Arjun, so does the fire of knowledge burn to ashes all reactions from material activities.

Commentary

Even a spark of fire has the potential to become a major conflagration and burn down a huge heap of combustible material. In 1666, the Great Fire of London began as only a little flame in a small bakery, but as it grew it consigned to flames 13,200 houses, 87 churches, and most of the city offices.

We too have a heap of karmas attached to each of us, consisting of the reactions of the sinful and righteous deeds performed by us over infinite lifetimes. If we endeavor to exhaust these karmas by reaping their results, it will take many more lifetimes, and in the meantime further karmas will accumulate in an endless process. But Shree Krishna assures Arjun that knowledge has the power to burn our heap of karmas in this lifetime itself. That is because knowledge of the soul and its relationship with God leads us to surrender to him. When we surrender to God, he burns our stockpile of endless lifetimes of karmas and releases us from material bondage.